The present invention relates to dynamic linking of user applications with function sets or classes used by the user applications.
Libraries are groups of routines that perform functions that may be useful to a different program. It is common for software developers to design application programs to call library routines to perform functions. Libraries may be static or dynamic. Static (or statically linked) libraries are linked once to each application program that uses them during the development of the program, before the program is ever executed. Dynamic libraries, or dynamically linked libraries (DLL), on the other hand, are linked automatically to the calling application programs when such programs are executed (i.e., at “run time”). Dynamic libraries are commonly used because they allow an application program image to be much smaller (as it does not need to include the library functions) and are capable of being shared by multiple application programs. Therefore, different application programs may use a particular dynamic library at the same time, requiring only a single copy of the dynamic library in memory instead of requiring a copy for every program. Additionally, dynamic libraries allow easy substition of one version for another. For example, an old version of a dynamic library may be easily replaced with a new version by simply replacing the file containing the old version with a file containing the new version.
Typically, application program developers distribute new versions of a dynamic library on disks or CDs, or electronically over the Internet. Since many application programs cannot locate the latest application program upgrade on their own, user interaction is often required. For example, the user may search for updates, call the software developer to order new updates or use third party tools to locate updates. There are instances when a dynamic library file or other component library cannot be located on a user's system. As is the case with the upgrade operation, in a repair operation a user locates the library and performs the installation manually. Unlike the upgrade operation, however, the repair operation is not only time consuming but error prone, as the user might install an incorrect file or incompatible version of the file, or even install the file in the wrong location.
Similarly, automatically self-healing/upgrading application programs cannot prevent the installation of an incorrect or incompatible file. Even more problematic still, when a replacement for a missing library file cannot be located, the self-healing/upgrading application program may cease to function properly or quit operation altogether.